Measurement of Stress-Deforemation Characteristics for a Polypropylene Particle of Fluidized Bed Polymerization for DEM Simulation M. Horio, N. Furukawa, H. Kamiya and Y. Kaneko Department of Chemical Engineering Tokyo University of Agriculture & Technology Graduate School BASE Koganei, Tokyo 184-8588, Japan
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020703 measurement of stress deformation characteristics for a polypropylene particle of fluidized bed polymerization for dem simulation
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Measurement
of
Stress-Deforemation Characteristics
for a Polypropylene Particle
of Fluidized Bed Polymerization
for DEM Simulation
M. Horio, N. Furukawa, H. Kamiya and Y. Kaneko
Department of Chemical Engineering
Tokyo University of Agriculture & Technology
Graduate School BASE
Koganei, Tokyo 184-8588, Japan
The scale-up of fluidized bed polyolefine reactors tends to
accompany agglomeration troubles in the reactor.
The cause of such tendency may be enhanced by liquid
bridging, van der Waals interaction and/or electrostatic
interaction that may suppress heat release from particles.
The authors group ( Kaneko et al. (1999) , (2000) ) has
developed DEM simulation for polyolefine reactors and
demonstrated that even a slight change in the distributor
design can affect solid mixing and cause temperature
maldistribution in the bed.
Background
Background (continued)
In their simulation, however, the cohesive force was not
taken into account.
Surface roughness affects cohesive interaction.
(In our DEM simulation for sintering particles ( Kuwagi et al.
( 2000 ) ) we found that the surface roughness affects very
much the sintering behavior. In the surface force dominant
range, the force-deformation relationship in a very
microscopic sense may affect the cohesive interaction.)
Objectives: Preliminary screening of factors significant in
DEM simulation of PP reactors
1) DEM simulation of thermal behavior of a PP bed with and
without van der Waals force.
2) A microscopic measurement of the force-deformation
relationship chasing surface roughness effects.
DEM, the last 10 years
DEM: Discrete Element Method
Fluid phase: local averaging
Particles: rigorous treatment User friendly compared to Two Fluid Model & Direct
Navier-Stokes Simulation
•A new pressure/tool to reconstruct particle
reaction engineering based on individual
particle behavior
•Potential for more realistic problem definition/
solution
SAFIRE: Simulation of Agglomerating Fluidization for Industrial
Reaction Engineering
Normal and tangential component of F collision
and F wall
Surface/bridge force
Rupture joint h c
Attractive force F c
No tension joint
Normal elasticity k n
Normal dumping h n
Tangential dumping h t
k t Tangential elasticity
Friction slider m SAFIRE is an extended Tsuji-Tanaka model
developed by TUAT Horio group
SAFIRE (Horio et al.,1998~)
(Non-linear spring)
t
t n t x
x F F m = n t F F m >
dt dx
x k F n n n n n h - D =
dt dx
x k F t t t t t h - D = n t F F m
km g = h 2 ( )
( ) 2 2
2
ln ln
p + = g
e e
w/wo Tangential Lubrication
w/wo Normal Lubrication
Soft Sphere Model with Cohesive Interactions
I-H
1998
Ash
Melting
Olefine
Polymerization
PP, PE
Kaneko et al.
1999
Scaling Law
for DEM
Computation
Kajikawa-Horio
2000~
Natural Phenomena
Catalytic Reactions
CHEMICAL REACTIONS
Structure of
Emulsion Phase
Kajikawa-Horio
2001
FUNDAMENTAL LARGE SCALE SIMULATION
OTHER
AGGLOMERATION COMBUSTION
Coal/Waste
Combustion
in FBC
Spray
Granulation/Coating
Agglomerating
Fluidization
FB of
Solid Bridging
Kuwagi-Horio
1999
Tangential
Lubrication
Effect
Kuwagi-Horio
2000
Particles w/
van der Waals
Interaction
Iwadate-Horio
1998
Single Char
Combustion
in FBC
Rong-Horio
1999
Parmanently
Wet FB
Mikami,Kamiya,
Horio
1998
FB w/
Immersed
Tubes
Rong-Horio
1999
FB
w/ Immersed
Tubes :
Pressure Effect
Rong-Horio
2000
Particle-Particle
Heat Transfer
Rong-Horio
1999
Fluidized Bed DEM
Started from
Dry-Noncohesive Bed
Tsuji et al. 1993
Scaling Law
for DEM
Computation
Kuwagi-Horio
2002~
Lubrication
Force Effect
Noda-Horio
2002
SAFIRE
Achievements
700 800 900 1000 1100 1200 1300 0
5
10
15
20
25
30
Nec
k d
iam
ete
r 2
x
Calculated from surface diffusion model
Steel shot :d p =200 m m, H 2 , 3600s
d p =200 m m d p =20 m m
Temperature [K]
ne
ck d
iam
ete
r, 2
x
neck
(b) 1123K (a) 923K
ne
ck d
iam
ete
r ,
2x
neck
10 m m
SEM images of necks after 3600s contact
Neck diameter determined from SEM images
after heat treatment in H2 atmosphere
Experimental Data of Solid Beidging Particles
(Mikami et al , 1996)
Sintering of
steel
particles in
FBR
Model for Solid Bridging Particles
1. Spring constant: Hooke type (k=800N/m)
Duration of collision: Hertz type
2. Neck growth: Kuczynski’s surface diffusion model
D = D exp (-E /RT)
D =5.2x10 m/s, E = 2.21x10 J/mol (T>1180K)
3. Neck breakage
s = neck neck nc A F
t = neck neck tc A F
7 1
3 4 gd 56
/
= t r D T k
x g S
B
neck
0,s
0,s
s s -2 5
Kuwagi-Horio 1999
Kuwagi-Horio
6 m m
r g = 10 m m
Steel shot
200 m m
neck
Cross section
Surface Roughness and Multi-point Contact Kuwagi-Horio 1999